A method and apparatus for matching impedance magnitude and impedance phase for an acoustic-wave transducer load and an RF power source. The acoustic-wave transducer load has a load impedance magnitude and phase. The RF power source has a source impedance magnitude and phase. In one embodiment of the invention, a transformer matches the source and load impedance magnitudes. A capacitor, connected in series with the transformer, matches the source impedance phase to the load impedance phase.
Legal claims defining the scope of protection, as filed with the USPTO.
1. An apparatus, comprising: an RF power source to generate power signals at a megasonic frequency, the RF power source having a source impedance magnitude, and the power signals having a current waveform and a voltage waveform; an acoustic-wave transducer load to receive the power signals and produce acoustic cavitation at the megasonic frequency, the acoustic-wave transducer load having a load impedance magnitude different from the source impedance; and a matching circuit connected to the RF power source and the acoustic-wave transducer load, the matching circuit including an impedance-phase-adjusting capacitor connected in series with an impedance-magnitude-adjusting transformer, the impedance-magnitude-adjusting transformer to match the load impedance magnitude to the source impedance magnitude, and the impedance-phase-adjusting capacitor to match the phases of the current and voltage waveforms.
2. The apparatus of claim 1 , wherein the impedance-phase-adjusting capacitor is to provide capacitance to counteract inductance introduced by the impedance-magnitude-adjusting transformer and a transmission line.
3. The apparatus of claim 1 , wherein the megasonic frequency is between approximately 875 kHz to 975 kHz.
4. The apparatus of claim 1 , wherein the impedance-phase-adjusting capacitor is to adjust a phase-difference curve to provide near-optimal power transfer within a bandwidth of approximately 5 kHz.
5. The apparatus of claim 1 , wherein the acoustic-wave transducer load operates between an anti-resonance peak and a resonance peak of a resonance curve.
6. The apparatus of claim 1 wherein the impedance-magnitude-adjusting transformer is an autotransformer.
7. The apparatus of claim 6 wherein the turns ratio of the autotransformer is selected to produce a slope of the resonance curve nearly vertical over a bandwidth of frequencies.
8. The apparatus of claim 6 wherein the turns ratio of the autotransformer is selected to produce a peak in the resonance curve of approximately twice the impedance of the power source.
Cooperative Patent Classification codes for this invention. Click any code to explore related patents in that topic.
January 12, 2005
March 13, 2007
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